NuttX-6.1
---------

The 68th release of NuttX, Version 6.1, was made on April 10, 2011
and is available for download from the SourceForge website. The
6.0 release introduced a detach-able application environment to
build applications outside of the NuttX source tree. The primary
purpose of this release is to correct numerous build problems
introduced by that architectural change:

* In many newer environments, NuttX produced strange Makefile
errors but built correctly in older environments. A fix provided
by Rafael Noronha was incorporated and is reported to fix those
build problems.
* The apps/ directory build system would not handle Windows-native
toolchains due to obscure path formatting issues.
* And other problems as detailed in the Changelog.

Many additional changes were made in the 6.1 release for another
major architectural change: NuttX will now build as a separately
linked microkernel. In this build option the RTOS builds as a
kernel, applications build separately and interface with kernel via
system calls. Applications run in user mode and kernel logic users
in kernel-mode. This provides a secure environment for NuttX. This
feature is fully coded in NuttX-6.1, but has not been tested due
to higher priority tasks that have arisen.

Related to this change, support for the Cortex-M3 memory protection
unit (MPU) has been integrated with the NuttX kernel build to provide
an even higher level of security.

NOTE: This kernel build is an option; the default build configuration
is still the standard, flat, unsecured RTOS as in previous releases.

Additional new features in this release:

* Support for LPC17xx GPIO interrupts (with much support from
Decio Renno).
* Basic timer support for STM32 (Contributed by Uros Platise)
* A binfs file system. This is a tiny pseudo file system that
lets named applications to be viewed and accessed in NSH under
the /bin directory.
* An I2C-based driver for the LIS331DL MEMS motion sensor.
(Contributed by Uros Platise.)
* A configuration for the Embedded Artists LPCXpresso LPC1768 board.
* The user_initialize() interface has been removed.

And several bugfix associated with SD drivers, opendir(), signed
8-bit types (int8_t), and USB serial device. See the ChangeLog for
details.
